The invention provides a diesel generator with a vibration reducing seat and a vibration reducing control method of the diesel generator. The vibration reducing seat can automatically regulate the inherent frequency of the vibration reducing seat according to the working condition of the diesel generator to be prevented from generating resonance with the diesel generator, and therefore the vibration reducing effect of the diesel generator is improved. The diesel generator comprises the vibration reducing seat and a diesel generator body, the vibration reducing seat is composed of a water tank and a support box, a support plate is movably erected on the top of the support box, the diesel generator body is fixed to the support plate, the support plate and the support box form a closed cavity, and the cavity is communicated with the water tank through a flexible water pipe and a water pump which are located on the lower portion of the support box; the water pump is provided with a control unit, and the control unit is connected with a revolving speed sensor for detecting the revolving speed of a crank shaft and a water level detection unit for detecting the water level in the support box; the top face of the water tank is lower than the bottom face of the support box. The control unit controls work of the water pump according to the revolving speed of the crank shaft, so that the water level in the support box can rise along with increasing the revolving speed of the crank shaft.